Scaffolds are vital components in tissue engineering. The success of functional tissue or organ regeneration relies on the development of suitable scaffolds to direct three-dimensional growth. Normal cell proliferation in nature is a precisely controlled series of events that inherently relies on spatial and temporal organization. Culturing cells in two dimensions, i.e., on a glass or polystyrene substrate, overlooks many parameters known to be important for accurately reproducing cell and tissue physiology. Such two-dimensional growth is not an accurate representation of the extracellular matrix found in native tissue. Many complex biological responses, such as receptor expression, transcriptional expression, and cellular migration, are known to differ significantly in two-dimensional growth conditions versus native conditions.
Current techniques seek to create scaffold structures that resemble those found in nature. Scaffolds are three dimensional (3D) structures that possess the proper shape, size, architecture, and physical properties to provide structural support for cell attachment and subsequent tissue development. Structural properties, such as macroscopic shape (architecture), pore size, porosity, pore interconnectivity, surface area, surface chemistry, and mechanical properties, are critical considerations in the design of scaffolds for tissue engineering, particularly in the regeneration of large and complex tissues. Typically, a viable scaffold must have high porosity, appropriate stiffness, high degree of reproducible precision, and appropriate pore sizes for target-specific tissue development. Scaffolds are usually created with biodegradable polymers and hydrogels, and typically degrade over time as the tissue grows around it. As the tissue starts building its own extracellular matrix to support its structure and function, the scaffold degrades to avoid inhibiting further tissue growth.
Various fabrication techniques have been developed to create suitable scaffolds, including melt molding, fiber bonding, spin casting, solvent casting and particulate leaching. Although scaffolds produced from these conventional techniques can address individual issues (e.g., architecture, pore size, or porosity), there is still a need for constructing scaffolds in a way that can address multiple structural issues and can meet the structural, mechanical, and nutritional requirements necessary for cellular growth.